The present invention relates to a torque transmitting apparatus which is characterized by the ability to continuously measure the torque being transmitted.
A torque transmitting apparatus of the described type is disclosed in DE 39 07 707 and corresponding U.S. Pat. No. 5,058,438, and wherein the torque passes through two members which rotate about a common axis, and which are interconnected by several axially directed integral beams. A plurality of fork-like elements are connected to the two members, and to a transducer ring, and upon the transmission of torque between the two members, the transducer ring is axially displaced by means of the fork-like elements. This axial movement is effectively amplified by the construction of the fork-like elements, and the axial movement is measured by a displacement measuring device, which indicates the transmitted torque. With regard to further details, express reference is made to the above referenced patents, whose disclosures are expressly incorporated in the present application by reference.
For the known torque transmitter, it is important that the displacement measuring device includes two sensors, with both sensors measuring in the same direction, i.e., on the one hand against the surface of the transducer ring, and on the other hand against a reference surface on one of the two rotatable members. The transducer ring and the reference surface are each designed and constructed in the shape of a ring, with the reference surface being radially arranged inside the transducer ring. Further, it is essential that the surfaces of the transducer ring and the reference surface, against which the sensors of the displacement measuring device measure, are located in the torque-free condition in one plane.
However, the above described known torque transmitter is extremely problematic in practice, as regards its measuring accuracy and the reproducibility of the measured results. This becomes especially noticeable, when in operation either the arrangement of the transducer ring and reference surface, or the arrangement of the displacement measuring device with the sensors arranged therein, are rotated or tilted relative to other components. Such a tilting of, for example, the sensors results in a change of the distances between the sensors and the surfaces of the transducer ring and the reference surface, with the distances from the transducer ring or the reference surface respectively varying in a different manner. This falsifies the measured result, i.e., the torque which is determined via the presumed proportionality of the displacement, with respect to the transmitted torque.
It is therefore the object of the present invention to provide a torque transmitter of the described type wherein error-free and reproducible torque measurements are possible regardless of slight tiltings between the transducer ring, reference surface, and displacement measuring device.